Method for Welding Sheet Metal Parts

Abstract

A method for butt welding of flat metal blanks in a welding machine, where two metal blanks are placed on a conveyor unit by feed devices and secured by holding means. Two edges of two metal blanks to be welded together are placed together to form a butt joint with the smallest possible gap and then welded together using a welding laser. The gap width is measured and controlled by means of the measured values from the welding process. The gap width is measured by means of the reflected-light method and the true gap width by means of the transmitted light method in such a way that the missing area and the missing volume in the gap can be estimated accurately.

Claims

1-12. (canceled)

13. A method for butt welding of adjacent edges (4, 5) of flat metal blanks (1, 2) in a welding machine, comprising: providing two flat metal blanks (1, 2) to be welded together; placing the two metal blanks (1, 2) on a conveyor unit (37) and securing them in a respective position with a first edge (4) of one of the metal blanks (1, 2) and an adjacent second edge (5) of the other of the metal blanks (1, 2) having a smallest possible gap therebetween; and welding the adjacent first and second edges (4, 5) together using a welding laser (6) to form a butt joint, wherein a gap width (7) between the first edge (4) and second edge (5) is measured and controlled via measured values from the welding process, the gap width (7) is measured via a reflected-light method wherein light rays (13, 14, 15, 16) from one or more light sources (11, 12) are reflected between the first and second edges (4, 5) and at least one reflected light ray (13) is captured by a camera, a true gap width (9) equal to the minimum distance between the respective edges (4, 5) is measured simultaneously by a transmitted light method wherein light (17) from a light source (18) is transmitted through the gap from above or below and is captured by a camera (20) from below or above, respectively, and the gap width (7) measured via the reflected-light method and the true gap width (9) measured via the transmitted light method are used to estimate a missing area (8) or missing volume in the gap.

14. The method according to claim 13, wherein the reflected-light method is a laser line method.

15. The method according to claim 14, wherein the laser line method is a laser triangulation method.

16. The method according to claim 13, wherein filler wire (10) is fed to the laser welding process (35).

17. The method according to claim 16, wherein the filler wire feed is controlled according to the estimated missing volume.

18. The method according to claim 13, wherein the measured gap width (7) and true gap width (9) results are analyzed using imaging techniques during the welding process in order to estimate the missing volume between the two edges (4, 5).

19. The method according to claim 17, wherein the measured gap width (7) and true gap width (9) results are analyzed using imaging techniques during the welding process in order to estimate the missing volume between the two edges (4, 5).

20. The method according to claim 18, wherein one or more holes in a weld of the butt joint are detected after the welding process via a light (31, 31) and corresponding camera (22, 23).

21. The method according to claim 13, wherein one or more holes in a weld of the butt joint are detected after the welding process via a light (31, 31) and corresponding camera (22, 23).

22. The method according to claim 17, wherein one or more holes in a weld of the butt joint are detected after the welding process via a light (31, 31) and corresponding camera (22, 23).

23. The method according to claim 13, wherein the reflected-light method uses light sources (11, 12) for monochromatic light.

24. The method according to claim 13, wherein the gap width (7) and the true gap width (9) are measured and analysed continuously throughout the welding process.

25. The method according to claim 17, wherein the gap width (7) and the true gap width (9) are measured and analysed continuously throughout the welding process.

26. The method according to claim 18, wherein the gap width (7) and the true gap width (9) are measured and analysed continuously throughout the welding process.

27. The method according to 13, characterized in that the reflected-light method and transmitted light method utilize at least one shared camera (20).

28. The method according to claim 13, wherein the reflected-light method is used to measure the gap width (7) on an upper side and an opposite lower side of the metal blanks (1, 2).

29. The method according to claim 14, wherein the reflected-light method is used to measure the gap width (7) on an upper side and an opposite lower side of the metal blanks (1, 2).

30. The method according to claim 13, wherein the transmitted light method is used to measure the true gap width (9) on an upper side and an opposite lower side of the metal blanks (1, 2).

31. The method according to claim 17, wherein the transmitted light method is used to measure the true gap width (9) on an upper side and an opposite lower side of the metal blanks (1, 2).

32. Use of the method of claim 13, wherein the flat metal blanks are used to produce tailored blanks for use in manufacturing a car body.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The present invention and also the problems of current measuring methods are explained further in the following using the embodiment examples and referring to drawings. In the drawings,

[0034] FIG. 1 shows an example of the disclosed laser welding process, in a side view as a schematic diagram;

[0035] FIG. 2 shows the edge of a metal sheet in cross section after the cutting process;

[0036] FIG. 3 shows possible shapes of cutting edges, in cross section as a schematic diagram;

[0037] FIG. 4 shows the gap between two metal blanks that are touching each other (without true gap), in cross section as a schematic diagram;

[0038] FIG. 5 shows a schematic diagram of two metal blanks in cross section that are not touching, with true gap and gap lighting according to the state of the art;

[0039] FIG. 6 in turn shows gap measurement by means of transmitted light, as a schematic diagram; and

[0040] FIG. 7 shows the gap between two metal blanks that are not touching each other, in cross section as a schematic diagram.

DETAILED DESCRIPTION

[0041] The same reference numerals in the respective figures refer to the same characteristics in each case.

[0042] FIG. 1 shows an example of an embodiment of the laser welding process 35 according to the invention for processing metal blanks 1, 2, which are placed on a conveyor unit 37 that can be moved in transport direction TR. In a first process step, the metal blanks 1, 2 are placed on the conveyor unit 37 by means of feed devices (not shown) and held there by means of holding means (not shown). After this, the gap position and the gap width are determined. This is achieved with the help of the top camera 20, optionally also with the bottom camera 21. In addition, a bottom light 18 and a top light 19 are provided opposite each of the two cameras 20, 21.

[0043] The space D between the two metal blanks 1, 2 depends on the layout of the metal blanks to be welded, where D can be kept small if the metal blanks 1, 2 have a rectangular layout and can be selected to be larger if the metal blanks 1, 2 have a rhomboid layout. In a second process step, the metal blanks 1, 2 are joined to form a welded metal blank 36 by laser welding 6, with a filler wire 10 being added by the filler wire unit 24. In a third process step, the quality of the weld seam is checked from above with a stationary, second quality system comprising a top camera 22 and a bottom light 31 and, as an option, from below with an additional, stationary quality system (bottom camera 23 and top light 32). Subsequently, the welded metal blank 36 is removed from the conveyor belt after the holding means (not shown) has been detached.

[0044] FIG. 2 shows an example of the edge 5 of a metal blank 1 after cutting, with sheet thickness T1, as a schematic diagram. As a result of the cutting process, the edge 5 has the roll-over area R after plastic deformation, the non-deformed cutting area S, the fracture area B and the burr G. The ratio of S to B can vary considerably.

[0045] FIG. 3 shows possible cutting edge shapes and different gap geometries as a schematic diagram. If a left-hand metal blank 1 and a right-hand metal blank 2 are pushed against one another, the gap geometry between the two metal blanks 1, 2 can change from one blank to the next due to plastic deformation of the edges during the cutting process. In addition, the gap geometry depends upon whether the sheet thicknesses T1, T2 of the two metal blanks are the same or not. It is also clearly shown here that the gap geometry changes considerably depending on the position of the metal blanks 1, 2. If the two upper sides of the metal blanks 1, 2 in the cutting process also face upwards during the welding process, the gap geometry is completely different to when one or both of the sides facing upwards in the cutting process are facing downwards during the welding process.

[0046] FIG. 4 shows a schematic diagram with a left-hand metal blank 1 in cross section, with sheet thickness T1, with the upper side 25 and the lower side 26, and a right-hand metal blank 2 in cross section, with sheet thickness T2, with the upper side 25 and the lower side 26. The two metal blanks 1, 2 are touching at the bottom in the roll-over area on the left 27 and the roll-over area on the right 28. Thus, there is no gap (no true gap) in this area. The gap width 7 is determined with the gap measuring device using the reflected-light method according to the state of the art. This gap width 7 determined usually reflects the gap width in the upper part of the gap. The shaded area depicts the missing area 8 between the two metal blanks 1, 2. As the gap closes here in the lower area, the missing area 8 can only be estimated very roughly by means of the gap width 7 measured.

[0047] FIG. 5 shows a gap measuring device using the reflected-light method. The two metal blanks 1 and 2 are not touching here, hence there is a true gap. A true gap is understood as being the gap width equal to the minimum distance between the two edges 4 and 5 of the metal sheet when viewed in cross section. Two light sources 11, 12 illuminate the true gap, the light ray 13 reflected several times being received by the camera 20. The light ray 14 is reflected in the upper area of the left-hand edge 4 in such a way that it cannot be captured by the top camera 20. Light ray 15 and light ray 16 are reflected several times in the area of the left-hand edge 4 and the right-hand edge 5, but also cannot be captured by the camera 20. With this process, the gap width 7 is determined in the upper area of the metal blanks 1, 2, however, this generally is not the same as the true gap width.

[0048] FIG. 6 now shows the gap measuring device using the transmitted light method at two metal blanks 1, 2 with true gap. Hence, the left-hand metal blank 1 with sheet thickness T1, with the upper side 25, the lower side 26, and the edge 4, and the right-hand metal blank 2 with sheet thickness T2, with the upper side 25, the lower side 26, and the edge 5, are not touching. The bottom light 18 shines light 17 from below through the gap, and this light is captured by the top camera 20. This gap measuring device using the transmitted light method measures the true gap width 9, which is the minimum distance between the two edges 4 and 5.

[0049] FIG. 7 now shows the gap measuring device according to the disclosure. Here, the gap is measured using the reflected-light (as shown in FIG. 5) and the transmitted light method (as shown in FIG. 6) at the same time. The two metal blanks 1, 2 are not touching in the present example. The gap width 7 is measured in the upper area of the metal blanks 1 and 2 using the reflected-light method. The true gap width 9 is determined using the transmitted light method.

[0050] In the present example, the light rays from the reflected-light and the light rays from the transmitted light method are captured by a shared camera 20. If the true gap width 9 is deducted from the gap width measured 7, the false gap width 3 is obtained. The false gap area 29 is the gap area underneath the false gap width 3. The false gap area 29 can be estimated using the false gap width 3 and the sheet thickness T1, T2. The true gap area 30 can be determined using the true gap width 9 measured and the known sheet thicknesses T1, T2. The sum of the estimated false gap area 29 and the true gap area 30 determined adds up to the missing area 8 and can be used to estimate the missing volume.

[0051] In FIG. 1, the reflected-light method is used not only on the upper side of the metal blanks 1, 2 but also on the lower side. There are two light sources 38 and 39 located underneath the metal blanks for this purpose. The light rays from the light sources 38, 39 are reflected off the metal blanks and the gap and captured by the bottom camera 21. Similarly, this camera 21 captures the transmitted light rays from the top light.

LIST OF REFERENCE NUMERALS

[0052] 1 Left-hand metal blank [0053] 2 Right-hand metal blank [0054] 3 False gap width [0055] 4 Sheet metal edge [0056] 5 Sheet metal edge [0057] 6 Welding laser [0058] 7 Gap width measured using the reflected-light method [0059] 8 Missing area [0060] 9 True gap width [0061] 10 Filler wire [0062] 11, 12 Light sources [0063] 13 Light ray [0064] 14 Light ray [0065] 15 Light ray [0066] 16 Light ray [0067] 17 Light [0068] 18 Bottom light [0069] 19 Top light [0070] 20 Top camera [0071] 21 Bottom camera [0072] 22 Top camera [0073] 23 Bottom camera [0074] 24 Filler wire unit [0075] 25 Upper side of metal blank [0076] 26 Lower side of metal blank [0077] 27 Roll-over, left [0078] 28 Roll-over, right [0079] 29 False gap area [0080] 30 True gap area [0081] 31 Bottom light [0082] 32 Top light [0083] 35 Laser welding process [0084] 36 Welded blank [0085] 37 Conveyor unit [0086] 38, 39 Light sources [0087] TR Transport direction [0088] R Roll-over area [0089] S Cutting area [0090] B Fracture area [0091] G Burr [0092] D Distance between metal sheets [0093] T1 Sheet metal thickness, left-hand blank [0094] T2 Sheet metal thickness, right-hand blank